68 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



I. Monongahela River system. 



a. Greene County group of Upper Barren measures. 

 &. Washington County group of Upper Barren measures. 

 c. Upper Productive Coal Measures. 

 II. Allegheny River system. 



a. Lower Barren measures. 



o. Mahoning sandstone. 



e. Lower Productive Coal Measures. 



the plane between the two s}^stems being drawn at the bottom of the 

 Pittsburg coal bed.* But the geographical terms were abandoned 

 quickly, and in later volumes of the reports the terms Upper and Lower 

 barrens, Upper and Lower Productive Coal Measures were used instead, 

 the Mahoning sandstone in most of the reports being included in the 

 Lower Productive Coal Measures. 



In 1891 Doctor I. C. White introduced the term Dunkard to designate 

 the Upper Barren measures, the Greene and Washington County groups 

 of Pennsylvania, Eeport K, and at the same time limited the term Monon- 

 gahela to the Upper Productive Coal Measures. f 



The synonymy may be given as follows in ascending order : 



Coal Measures, XI II of H. D. and W. B. Rogers 



Allegheny Allegheny of H. D. Rogers in part ; XIII, 



F. Piatt, 1875. Lower Coal group of W. B. Rogers less the 



Mahoning sandstone; Lower series of Les- 

 ley; Lower productive series of Stevenson 

 less the Mahoning; Lower Coal Measures 

 of Ohio in part ; Lower group of H. D. 

 Rogers. 



Conernaugh Barren measures of Lesley plus the Mahon- 



F. Piatt, 1875. ing sandstone; Lower shale and sandstone 



group of W. B. Rogers plus the Mahoning ; 

 Lower Barren series of Stevenson plus the 

 Mahoning; Lower Coal Measures of Ohio, 

 upper part ; Middle group of H. D. Rogers. 



Monongahela Middle portion of Monongahela of H. D. 



I. C. White, 1891. Rogers ; Lower portion of Monongahela of 



F. Piatt ; Upper productive series of Steven- 

 son; lower portion of Upper series of Les- 

 ley ; in part XV, Upper Coal group of W. B. 

 Rogers ; lower portion of Upper Coal Meas- 

 ures of Newberry ; lower division of Greene 

 County group of H. D. Rogers. 



* F. Piatt : Report H H, pp. xxiii. xxiv. 



t I. C. White : U. S. Geol. Survey Bulletin no. Go, pp. 20, 43. 



